1. Field of the Invention
The present invention relates to host-based ink jet printers, and, more particularly, to a method of transmitting raster information from the host computer to the ink jet printer and thereafter printing with the printer using the transmitted raster information.
2. Description of the Related Art
Ink jet printers commonly include a printhead which is mounted on a carriage assembly. The carriage assembly is movable in a transverse direction, relative to an advance direction of a print medium such as paper. As the printhead is moved across the print medium during a particular pass of the carriage assembly, ink is selectively jetted from ink jetting orifices formed in the printhead and is deposited on the print medium at corresponding ink dot placement locations. Since the printhead moves in a direction transverse (e.g., perpendicular) to the advance direction of the print medium, each ink emitting orifice passes in a linear manner over the print medium. The line associated with each ink emitting orifice which overlies the print medium is commonly referred to as a raster. A plurality of rasters which extend across the image area of the print medium are disposed vertically adjacent to each other in the advance direction of the print medium.
Multi-color ink jet printers typically include a printhead having a plurality of ink emitting orifices therein. The ink emitting orifices are segregated into different arrays of ink emitting orifices, with each array corresponding to the different color inks which are to be jetted onto the print medium. With a known tri-color printhead, a first array of ink emitting orifices is used for jetting yellow ink onto the print medium, a second array of ink emitting orifices is used for jetting magenta ink onto the print medium, and a third array of ink emitting orifices is used for jetting cyan ink onto the print medium. The first, second and third arrays of ink emitting orifices are sequentially arranged relative to the advance direction of the print medium. Associated with each ink emitting orifice in the three arrays of ink emitting orifices is a corresponding ink jetting heater. Actuation of a particular ink jetting heater causes the formation of a bubble within the ink disposed adjacent thereto and expels the ink from the associated ink emitting orifice. The host computer transmits raster information to the printer for selective actuation of the ink jetting heaters.
With a tri-color printhead as described above, it is known to transmit raster information from the host computer to the printer such that raster information for each array of the printhead is simultaneously received. For example, assuming that each array of ink emitting orifices in the tri-color printhead corresponds to eight rasters on the print medium, it is known to transmit raster information for eight rasters of yellow, eight rasters of magenta and eight rasters of cyan prior to the first pass of the printhead. Since the yellow, magenta and cyan ink is sequentially rather than simultaneously jetted onto the rasters of the print medium, only the raster information corresponding to the yellow array of ink jetting heaters is actually used during the first pass of the printhead. The raster information for the magenta and cyan ink jetting heaters must therefore be stored in memory until used during subsequent passes of the printhead. The printer must thus include a capability of storing, sorting and retrieving the additional raster information as needed.
Although a technique of transmitting raster information from the host computer to the printer as described above typically is adequate, it is not optimum from an efficiency standpoint and results in a printer with an oversized memory capacity. An increase in the memory capacity of the printer in turn may increase the cost and complexity of the printer.
What is needed in the art is a method of more efficiently transmitting raster information from the host computer to the ink jet printer, and thereafter printing on the print medium using the transmitted raster information.